2(g) Gas exchange
11 specification points in sub-topic 2(g).
Specification points
2.40B: Diffusion in plant gas exchange
How oxygen, carbon dioxide and water vapour diffuse in and out of leaves.
2.41B: Gas exchange, respiration and photosynthesis
How photosynthesis and respiration together decide which gases a plant takes in and gives out.
2.42B: Leaf adaptations for gas exchange
How a leaf’s thin shape, air spaces and stomata speed up gas exchange.
2.43B: Stomata and gas exchange
How guard cells open and close stomata, balancing gas exchange against water loss.
2.44B: Net gas exchange in light and dark
Why plants give out carbon dioxide at night but take it in during bright daylight.
2.45B: Light and net gas exchange
Practical: using hydrogencarbonate indicator to show how light affects gas exchange in a leaf.
2.46: Structure of the thorax
The structure of the thorax: airways, lungs, ribs, intercostal muscles and diaphragm.
2.47: Ventilation
How the diaphragm and intercostal muscles change lung volume and pressure to move air.
2.48: Alveoli and gas exchange
How alveoli are adapted for fast diffusion of oxygen and carbon dioxide.
2.49: Biological consequences of smoking
How smoking damages the airways, alveoli, blood and heart.
2.50: Breathing in humans
Practical: carbon dioxide in breathed-out air, and how exercise changes breathing rate.